302 CLASS ASCOMYCETEAE 



Perithecia buried in a stroma, ascospores as above. Family Hypocreaceae 



Hypocrea, Polystigma, Hypomyces. 

 Perithecia buried in a stroma with poorly developed perithecial walls, sometimes 

 only slightly developed near the ostiole. Ascospores filiform. 



Family Clavicipitaceae' 

 Cordyceps, Claviceps, Balansia, Epichloe. 



Key to Some Families of Order Pyreniilales* 



Perithecia opening through round ostioles; not embedded in a stroma. 



Perithecium more or less immersed in the crustose thallus. Paraphyses remain- 

 ing distinct. Algal host Trentepohlia. Mostly on trees, rarely on rocks. 



Family Pyrenulaceae 

 Pyrenula. 

 Perithecia more or less immersed in the crustose thallus. Paraphyses mostly gela- 

 tinizing early. Algal host Pleurococcus. Mostly on rocks, rarely on trees. 



Family Verrucariaceae 

 Verrucaria. 

 Perithecia immersed in the squamulose or foliose thallus. Paraphyses gelatiniz- 

 ing early. Algal host Pleurococcus. Mostly on soil or rocks. 



Family Dermatocarpaceae 

 Dermatocarpon. 

 Perithecia embedded in a stroma. Thallus crustose. Algal host Trentepohlia. 

 Perithecia opening separately through round ostioles. Paraphyses remaining 

 distinct. On trees. Family Trypetheliaceae 



Trypethelium. 

 Perithecia arranged radially in the stroma with the ostiolar necks converging 

 and opening separately or through a common ostiole. Paraphyses remain- 

 ing distinct. Mostly on trees. Family Astrotheliaceae 

 Astrotheliuni. 

 Perithecia in groups of two (rarely one) or more, the intervening walls sometimes 

 partially missing; the large, irregular ostiole sometimes serving two or more 

 perithecia. Paraphyses poorly developed or disappearing early or persist- 

 ing. Thallus crustose. Algal host Palmella or TrentepohHa. On trees. 



Family Mycoporaceae 

 Mycoporum. 



Key to the Families of Order Dothideales 



Only recognized family.* Family Dothideaceae 



Dothidea, Dothidella, Systremma. 



Key to the Families of Order Pseudosphaeriales 



Stromata small, internal or eventually external, perithecium-like. Asci more or 



less parallel, formed in moiiascal cavities which long remain separate by 



the persisting intervening stromatal tissues which connect from the base 



to the top of the stroma. Family Pseudosphaeriaceae 



Pyrenophora, Dothiora. 



* Careful studies are needed to determine whether the ascocarps in this order are 

 true perithecia or pseudoperithecia. The distinction of families as usually made is 

 largely l)ased on the kinds of algal hosts as well as the habit of the thallus. Only part 

 of the 10 or more families are mentioned in this key. 



*F()r Phyllachoraceae, see Order Sphaeriales. 



